Rear aperture sight for rifle

ABSTRACT

A rear aperture sight for use in conjunction with a front sight post sight on a rifle. The front sight post has a horizontal top edge and vertical side edges. The rear aperture sight comprises a rear sight adapted to be mounted on the rifle. The rear sight has a horizontally elongated aperture formed therein having height and width dimensions. The width dimension is greater than the height dimension. The aperture is defined by two circular segments s 1  and s 2  having chords c 1  and c 2 , respectively, defined by included angles θ 1  and θ 2 , respectively, of circles having radii R 1  and R 2 , respectively. The chords c 1  and c 2  have heights h 1  and h 2 , respectively. Radii R 1  and R 2  and angles θ 1  and θ 2  are selected such that chords c 1  and c 2  are of equal length. The circular segments are positioned such that chords c 1  and c 2  are co-linear and oriented horizontally. In another aspect, the rear sight has at least one aperture plate having an aperture formed therein which defines an entrance pupil for an eye of a shooter of the rifle. The entrance pupil is horizontally elongated having a height h and a width w, the width w being at least about 125% of the height h, the height h being smaller than a diameter of a pupil of the eye of the shooter and of such a value that the entrance pupil is adapted to cause the horizontal top edge of the front sight post and a horizontal edge of a target to be more sharply focused than if viewed by an unaided eye, the width w being of such a value that an area defined by the entrance pupil is greater than an area defined by a circular entrance pupil having a diameter equal to the height h, thereby permitting more light to pass through the entrance pupil than through the circular entrance pupil, and causing the front sight post and the target to appear brighter than if viewed through the circular entrance pupil.

RELATED APPLICATIONS

This application is a continuation-in-part of application Ser. No. 11/957,963, which is a continuation-in-part of application Ser. No. 11/619,953, and a continuation-in-part of application Ser. No. 11/619,953, both of which are hereby incorporated by reference herein as if fully set forth in their entirety.

FIELD OF THE INVENTION

This invention relates generally to firearms, and more particularly to sighting systems for firearms.

BACKGROUND OF THE INVENTION

The depth of field of an optical system, including the human eye, is defined in part by the diameter of the “entrance pupil” to that optical system. The entrance pupil diameter is that dimension which is used, along with a lens focal length, to calculate a lens f-ratio, and which is in turn used to calculate depth of field. An entrance pupil is the projection along the optical axis, towards the first lens surface of an optical system, of an aperture which limits the entry of light beams into that optical system. For the human eye, the first lens surface is the surface of the cornea, and the entrance pupil of the unaided eye is the forward projection of the eye's pupil along the optical axis of the eye onto the cornea. Since the cornea is a converging lens, and the pupil is located slightly behind the surface of the cornea, the entrance pupil to the unaided eye is slightly larger than the true opening in the pupil. To an outside observer, the viewed size of the pupil of the eye is the entrance pupil size, the true size of the pupil being slightly smaller. For the purpose of this application, the size of the eye's pupil, and the size of the entrance pupil, created by the projection of the eye's pupil forward onto the cornea, can be treated as the same, and will be used interchangeably.

If an external aperture is placed in front of the eye, along the optical axis of the eye, it is the projection of the open area of that aperture, along the optical axis of the eye, onto the cornea, that defines the entrance pupil created by the external aperture. If several non-overlapping apertures are present in an optical system, each defining an entrance pupil, the smallest of the non-overlapping entrance pupils is the dominant entrance pupil which drives the depth of field of that optical system. Thus, if a round aperture is placed on the optical axis of the eye, in front of the eye, and if the opening of the aperture is oriented perpendicular to the axis of the eye, and if the diameter of the entrance pupil, created by projecting the aperture along the axis of the eye onto the cornea, is larger than the entrance pupil created by the eye's pupil, the eye's pupil, being smaller than the projection of the larger round aperture, will be the dominant entrance pupil of the eye.

If a round aperture is placed on the optical axis of the eye, in front of the eye, and its opening is oriented perpendicular to the axis of the eye, and the aperture diameter is smaller than the pupil of the eye, and therefore the entrance pupil created by that aperture is smaller than the entrance pupil created by the pupil of the eye, it will then be the external aperture, and not the eye's pupil that creates the dominant entrance pupil to the eye.

If several apertures, whose open areas overlap each other, are present along the optical axis of the eye, it is the projection of their common open area, along the optical axis of the eye, onto the cornea surface, that will define the entrance pupil created by those apertures. If the entrance pupil created by the eye's pupil is larger than the entrance pupil created by the common open areas of the apertures, the common open area of the apertures will be the dominant entrance pupil for the viewer.

If an irregularly shaped aperture is placed along the optical axis of the eye, in front of the eye, and is oriented with its opening perpendicular to the axis of the eye, the projection of that irregular aperture, along the axis of the eye, onto the cornea, will form an irregularly shaped entrance pupil of substantially the same dimensions and form as the irregularly shaped aperture itself. If the irregularly shaped entrance pupil created by the irregularly shaped aperture is smaller than the entrance pupil created by the eye's pupil, it is the irregularly shaped entrance pupil that will dominate the optical system of the eye.

If an irregularly shaped aperture is placed on the optical axis of the eye, in front of the eye, and its opening is oriented perpendicular to the axis of the eye, and the irregular aperture shape is such that the irregularly shaped entrance pupil created by the irregularly shaped aperture overlaps the entrance pupil created by the eye's pupil, it is the common open area of the irregularly shaped entrance pupil from the external irregularly shaped aperture, and the entrance pupil from the eye's pupil that will become the dominant entrance pupil for the viewer.

If an external aperture is placed along the optical axis of the eye, and such aperture is inclined to the optical axis of the eye, the entrance pupil created by the external aperture will be the projection of the open area of the inclined aperture along the optical axis of the eye onto the surface of the cornea. If the projection of the inclined aperture opening along the axis of the eye onto the cornea is smaller than the projection of the eye's pupil onto the cornea, the projected opening of the aperture will determine the entrance pupil of the eye. If the projection of the inclined aperture along the optical axis of the eye onto the cornea of the eye overlaps the projection of the eye's pupil onto the cornea, it is the common open area of the projection of the inclined aperture and the eye's pupil that will define the entrance pupil to the eye.

The depth of field for an optical system is defined relative to the plane in which the optical system is referenced. The degree to which an image can blur vertically is driven by the vertical dimension of the entrance pupil, while the degree to which an image can blur horizontally is driven by the horizontal dimension of the entrance pupil. The traditional paradigm of photography, and our experience with our own human vision, has the entrance pupil as being substantially round and perpendicular relative to the axis of the eye, thus blur in a photograph, or the eye, is typically equal in all directions. If the entrance pupil is not round, it is possible to have different depths of field, and different widths of resulting blur, in differing axes of the image. Examples of such an optical system are the pupils of cat's eyes, where the vertical slit shaped pupil will cause a greater depth of field in the horizontal direction, with less depth of field in the vertical direction. In the field of opthalmology, non-round entrance pupils are also created, using stenopaeic slits. These slits are narrower than the eye's pupil in one axis, but much wider than the pupil in the other axis, so as to create an increased depth of field only in 1 axis of the eye. By rotating the slit, the axis of a patient's astigmatism can be diagnosed.

The brightness of an image being viewed by the human eye is a function of the open area of the entrance pupil. If the entrance pupil is small, less light is able to pass, and the image will be dim. If the entrance pupil is large, more light will pass, and the image will be bright. If no smaller aperture is present, the pupil of the human eye will define a round entrance pupil, of varying diameter, depending on the brightness of ambient light. A typical human pupil in a well lit environment, outdoors, but not exposed to direct sun, is approximately 0.125 inches diameter. Since the pupil is close to the cornea surface, the entrance pupil defined by a 0.125 inches diameter pupil will also be approximately 0.125 inches.

In summary, if an aperture smaller than the pupil is placed along the eye's optical axis, in front of the eye, the smaller aperture will define the entrance pupil of the eye, and drive the depth of field of the eye, as well as the brightness of the image seen by the eye. If an aperture larger than the pupil is placed in front of the eye, the pupil will define the entrance pupil of the eye, and the aperture will not drive the depth of field of the eye, or the brightness of the image.

The United States military issues for service a pair of shoulder fired rifles, both chambered for the 5.56 mm NATO cartridge. One is designated the M16A2/M16A3/M16A4 rifle and the other is designated the M4/M4A1 carbine. Both weapons utilize a common sighting system comprising a rear sight having a leaf style aperture plate with a circular aperture therein and a front sight post. To properly aim the weapon, the horizontal top edge of the front sight post is centered horizontally and vertically on the target, and is also centered in the rear aperture.

Both weapons utilize a rear flip type dual leaf sight having two different aperture sizes from which to choose: a smaller aperture having a diameter of about 0.070 inches for longer ranges, and a larger aperture having a diameter of about 0.200 inches for shorter ranges, a greater field of view, and faster target engagement. The shooter flips the sight leaf having the correct aperture up into view based on the distance to the target. The larger aperture is for near targets, generally less than 200 meters, and the smaller aperture is for distant targets, generally greater than 200 meters.

The larger aperture permits a shooter to locate the front sight post and target in the rear aperture quicker than does the smaller aperture. Hence its suitability for near targets, wherein engagements are quicker. The smaller aperture does not permit the shooter to locate the front sight post and target therein as quickly as the larger aperture, but it does provide for more accurate aiming which is necessary at longer ranges. This is because the smaller aperture acts as a pinhole opening, creating a smaller entrance pupil to the eye, and improving the shooter's depth of field. The small vertical dimension of the smaller entrance pupil causes the horizontal top edge of the front sight post and any horizontal edges on the target to be more clearly focused, and the small horizontal dimension of the smaller entrance pupil causes the vertical side edges of the front sight post, and any vertical edges on the target, to be more clearly focused. This is in contrast to the larger aperture which does not focus the horizontal top edge of the front sight post, the vertical side edges of the front sight post, or the target as much, so they remain somewhat blurry to the shooter. Again, the larger aperture is for near targets, and so speed in aiming is paramount; even though the horizontal top edge and vertical side edges of the front sight post, and the target, are blurry, the sight picture is nonetheless sufficient to obtain accurate hits at closer ranges.

A distinct disadvantage in using the smaller rear circular aperture is that less light is permitted to pass through the aperture. Thus, even though the horizontal top edge and vertical side edges of the front sight post and target are clearly focused, which enhances accuracy in aiming and hence accuracy in shot placement, the front sight post and target are nevertheless dim, which hinders accuracy in aiming ability and hence accuracy in shot placement.

In the case of the M-16 and its aforementioned derivative designs, regardless of any adjustments made to the sight, the rear sight leaf is presented to the shooter at an angle substantially perpendicular to the bore of the rifle, so the axis of the aperture is presented substantially parallel to the optical axis of the shooter's eye. As a result, the entrance pupil created by the aperture is substantially identical to the shape and size of the aperture created in the aperture plate.

The United States military also issues for service a shoulder fired rifle, designated the M-14. This rifle is based on the famous M-1 rifle, designed by John Garand, and issued to US troops starting in WWII, with continued use through the Korea and Viet Nam eras. The M-1 rifle was lauded by Gen. George Patton as the “greatest battle implement ever devised”. Both of these weapons share a common sighting system comprising a front sight blade and a rear sight aperture plate 0.125 inches thick having a 0.069 inches diameter circular aperture formed therein. One side of the circular aperture is chamfered with a 30 degree included angle to a depth of 0.105 inches such that the straight portion of the aperture which is presented to the eye is only 0.020 inches deep. This aperture plate differs from the sight leaf seen on the M-16, and derivative models A2, A3, A4, M4, and M4-A1, or similar rifles, in that the aperture plate of the M-14 and M-1 is mounted in a track which follows a curved path. The arc of said track falls in the same plane as the bore of the rifle, but the curved track has a center of rotation set vertically above the aperture of the rifle, and closer to the muzzle than the aperture. In its lower, or “zero” position, used for engaging targets at under 200 yards, the aperture is oriented substantially perpendicular to the bore so the eye is looking along the axis of the aperture. In this position, the round 0.069 inches diameter aperture projects a round 0.069 inches diameter entrance pupil to the eye.

When the aperture of the M-1 or M-14 rifle is raised to engage targets at greater distances, its swing along the arc of the track in which it travels, moves the aperture not only up, but also causes it to incline forward. As the aperture travels through its full range of motion in the curved track, the aperture will elevate relative to the bore of the rifle, which is the desired consequence to allow a rifle to be aimed at a greater distance, however due to the curved track, the aperture plate also pivots forward up to approximately 15 degrees relative to the shooter, so the aperture is presented to the eye at a 15 degree forward inclination to the bore. In the case of maximum inclination of the aperture leaf to the bore, the 0.020 inches deep by 0.069 inches diameter round aperture presents the eye with an entrance pupil which is a vertically compressed slit, made up of two elliptical arcs, and has dimensions of 0.069 inches wide×0.061 inches tall, so the height of the entrance pupil measured perpendicular to the bore is reduced by approximately 12% versus the diameter of the aperture as measured parallel to the aperture face. In this configuration, if the width of the entrance pupil is calculated as a function of its height, it can be said that the width is 113% of the height.

To properly aim any of the above described weapons, the horizontal top edge of the front sight post is centered horizontally and vertically on the target, and is also centered in the entrance pupil that is created by the aperture. In this configuration, the shooter's line of vision is substantially parallel to the bore. There is a small difference between the true axis of the bore, and the true line of sight of the shooter's eye when the eye is correctly aligned on the target. This small difference is due to the fact that the sights are offset from the bore, and also the difference in angle is adjusted to compensate for the drop of the bullet and wind drift during flight. The correct alignment of the sights is such that the line from the eye, through the center of the aperture, and past the top edge of the front sight will align with the point on the target where the bullet will impact. The correct alignment of the bore is such that it allows the bullet to be launched in a direction such that, allowing for wind drift and gravitational drop, the bullet will impact the target at the same point where the sights are pointed. The difference between the axis of the bore and the alignment of the sights is typically less than 1 degree, and in target shooting this difference is typically expressed in Minutes of Angle (MOA). In the following discussion, the small difference between these angles will be treated as being substantially zero. For the purposes of this discussion, the line of the sight of the shooter's eye while aiming a rifle will therefore be treated as being substantially parallel to the bore of the rifle.

In competition shooting with the U.S. service rifle, for example in NRA High Power rifle competition, it is customary to utilize a “6 o'clock hold.” This means that the horizontal top edge of the front sight post is placed at the bottom edge of the circular bull's eye of the target, i.e. at 6 o'clock. Experience has shown that the most important features to be in focus, for an accurate 6 o'clock hold, and hence, accurate target shooting, are the horizontal top edge of the front sight post, and the horizontal bottom edge of the target. The focus of the vertical side edges of the front sight post and of the vertical side edges of the target are less critical.

A problem with traditional round aperture sights is that once the aperture is reduced in size to provide optimal focus on the horizontal top edge of the front sight post and the horizontal bottom edge of the target, the amount of light passing through the opening is so limited that the target and the front sight post appear dim to the shooter. In other words, a sub-optimal focus must be accepted in order for the amount of light passing through the opening to be sufficient for the front sight post and target to appear bright to the shooter.

Accordingly, it is desirable to provide a rear aperture sight for a rifle which creates an entrance pupil to the eye that has a vertical dimension that is significantly smaller than the pupil, so as to cause the horizontal top edge of the front sight post and the horizontal bottom edge of the bull's eye to be as sharply focused as possible, but the entrance pupil must at the same time present the greatest amount of area to the shooter, so as to be the least restrictive of the amount of light able to pass through the aperture, so as to prevent the front sight post and target from being dim.

SUMMARY OF THE INVENTION

In one aspect, the present invention is a rear aperture sight for use in conjunction with a front sight post sight on a rifle, the front sight post having a horizontal top edge and vertical side edges. The rear aperture sight comprises a rear sight adapted to be mounted on the rifle. The rear sight has a horizontally elongated aperture formed therein having height and width dimensions. The width dimension is greater than the height dimension. The height dimension is of such a value that the aperture is adapted to cause the horizontal top edge of the front sight post and a horizontal edge of a target to be sharply focused. The width dimension is of such a value that the aperture is adapted to permit a sufficient amount of light to pass through the aperture so that the front sight post and the target are bright.

In another aspect, the invention is a rifle having a receiver and a barrel, and having the rear aperture sight and the front sight post sight of the above mounted on the receiver and barrel, respectively.

In another aspect, the invention is the combination of the rear aperture sight and the front sight post sight of the above.

The aperture of the rear sight can have a number of possible width-to-height aspect ratios, width and height dimensions, and shapes. The width dimension can be in a range of about 110% to about 500% of the height dimension; the width dimension can be in a range of about 120% to about 300% of the height dimension; the width dimension can be in a range of about 140% to about 160% of the height dimension. The height dimension can be in a range of about 0.010 inches to about 0.100 inches. The width dimension can be in a range of about 0.011 inches to about 0.20 inches. The aperture can be rectangular shaped, rectangular shaped with radiused corners, oval shaped, hexagonal shaped with vertices positioned at 3 o'clock and at 9 o'clock, and/or elliptical shaped. The rear sight can be a leaf sight.

The aperture can be defined by two arc segments s1 and s2, having identical chords c1 and c2, respectively, defined by included angles θ1 and θ2, respectively, of circles having radii R1 and R2, respectively. Radii R1 and R2 and angles θ1 and θ2 are selected such that chords c1 and c2 are of equal length. The circular segments are positioned such that the chords c1 and c2 are co-linear and oriented horizontally. In one aspect, R1=R2=R and θ1=θ2=θ. In another aspect, R1≠R2 and θ1 ≠θ2. In yet another aspect, w=c1=c2, where w is in a range of about 0.011 inches to about 0.20 inches, and h=h1+h2, where h is in a range of about 0.010 inches to about 0.100 inches. Alternatively the aperture can be defined by two overlapping circles having respective centers A and B, a distance between the centers A and B being AB, the overlapping circles having overlapping circular segments s1 and s2 which have chords c1 and c2, respectively, wherein the chords c1 and c2 are oriented vertically. In that case, w is equivalent to a sum of AB, R1, and R2, and h is equivalent to twice a greater of R1 and R2.

In another aspect, the present invention is a rear aperture sight for use in conjunction with a front sight post on a rifle, the front sight post having a horizontal top edge and vertical side edges. The rear aperture sight comprises a rear sight adapted to be mounted on the rifle. The rear sight has an aperture plate of some thickness with a round aperture of some dimension formed therein, the aperture axis is formed perpendicular to the face of the aperture plate, and the aperture plate is presented to the shooter in an orientation so the axis of the aperture is inclined at some angle to the rifle bore, and also to the optical axis of the eye. Due to the said inclination of the aperture axis, and also the thickness of the aperture plate, the open area of the aperture, projected along the optical axis of the eye onto the cornea, will create a horizontally elongated entrance pupil to the eye, said entrance pupil having height and width dimensions. The width dimension of the entrance pupil is greater than the height dimension. The height dimension of the entrance pupil is of such a value that the entrance pupil is smaller than the pupil of the eye, and will cause the horizontal top edge of the front sight post and horizontal edges of a target to be more sharply focused than if viewed with the naked eye, or if viewed through an identical aperture which were presented to the eye in an orientation so the axis of the aperture was substantially parallel to the bore of the rifle and the axis of the eye. The width dimension of the entrance pupil, being larger than the height dimension, will allow more light to pass through the aperture, so that the front sight post and the target are brighter, than if they were viewed through an entrance pupil which was round and with a diameter equivalent to the height dimension of the entrance pupil.

In another aspect, the present invention is a rear aperture sight for use in conjunction with a front sight post on a rifle, the front sight post having a horizontal top edge and vertical side edges. The rear aperture sight comprises a rear sight adapted to be mounted on the rifle. The rear sight has an aperture plate of some thickness with a round aperture of some dimension formed therein, the axis of the aperture opening is formed at an angle to the face of the aperture plate which is different from perpendicular. The aperture plate is presented to the shooter at an angle substantially perpendicular to the rifle bore, so the axis of the aperture is at an angle different from parallel to the optical axis of the eye. Due to the inclination of the aperture axis at said angle to the aperture plate, and the thickness of the aperture plate, the common open area of the aperture, projected along the optical axis of the eye onto the cornea, will create a horizontally elongated entrance pupil to the eye, said entrance pupil having height and width dimensions. The width dimension of the entrance pupil is greater than the height dimension. The height dimension of the entrance pupil is of such a value that the entrance pupil is smaller than the pupil of the eye, and will cause the horizontal top edge of the front sight post and a horizontal edge of a target to be more sharply focused than if viewed with either the naked eye. The width dimension of the entrance pupil, being larger than the height dimension, is of such a value that the open area of the aperture is adapted to permit a sufficient amount of light to pass through the aperture so that the front sight post and the target are brighter than if they were viewed through an entrance pupil which was round and with a diameter equivalent to the height dimension of the entrance pupil.

In another aspect, the present invention is a rear aperture sight for use in conjunction with a front sight post on a rifle, the front sight post having a horizontal top edge and vertical side edges. The rear aperture sight comprises a rear sight adapted to be mounted on the rifle. The rear sight has at least two aperture plates with apertures formed therein, each aperture having height and width dimensions, and all aperture plates are presented substantially perpendicular to the axis of the eye, but positioned such that the apertures are displaced relative to one another in a vertical direction that is radial to the axis of the bore, such that the projection of their common open areas along the axis of the eye onto the cornea creates an entrance pupil to the eye which is horizontally elongated, said entrance pupil having height and width dimensions. The width dimension of the entrance pupil is greater than the height dimension. The height dimension of the entrance pupil is of such a value that the entrance pupil is smaller than the pupil of the eye, and will cause the horizontal top edge of the front sight post and a horizontal edge of a target to be more sharply focused than if viewed with the unaided eye. The width dimension of the entrance pupil is of such a value that the aperture is adapted to permit a sufficient amount of light to pass through the aperture so that the front sight post and the target are brighter than if they were viewed through an entrance pupil which was round and with a diameter equivalent to the height dimension of the entrance pupil. Examples of aperture shapes which might be utilized in this example are two round apertures, whose vertically overlapped shapes would create a horizontally elongated slit shaped entrance pupil, like a cat's eye. Another example might be the vertical overlap of two square apertures, whose vertically overlapped shapes would create a horizontally elongated rectangular entrance pupil. Other aperture shapes can also be used, such that the effect of a vertical misalignment of the two apertures creates an entrance pupil which is horizontally elongated, relative to its height.

In another aspect, the present invention is a rear aperture sight for use in conjunction with a front sight post on a rifle, the front sight post having a horizontal top edge and vertical side edges. The rear aperture sight comprises a rear sight adapted to be mounted on the rifle. The rear sight has at least two aperture plates with apertures formed therein, the aperture plates having apertures of differing shapes. The aperture plates are presented to the eye such that the projection of their common open area along the axis of the eye onto the cornea forms an entrance pupil to the eye that is horizontally elongated, even though all apertures lie on the optical axis of the eye. For instance, an aperture of the shape of an equilateral triangle pointed “up” can be superimposed on an aperture of the shape of an equilateral triangle pointed “down.” The combination of their collective total areas would form a six pointed star, but the projection of only their common open areas along the axis of the eye onto the cornea would form a horizontally elongated hexagonal entrance pupil with vertices at 3 o'clock and 9 o'clock.

In another aspect, any of the afore described apertures can be created by adding an opaque mask to a transparent substrate, such as a lens, so as to create an aperture for light, without actually creating a hole in the aperture plate.

In another aspect, any combination of any of the above described aperture plates, with aperture holes of differing shapes, formed perpendicular to, or at an angle to the face of the aperture plate, can be presented along the axis of the eye with various aperture plates being presented perpendicular to the axis of the eye, and other aperture plates being presented at an inclination to the optical axis of the eye, and with some apertures being offset from the optical axis of the eye in a vertical direction perpendicular to the bore of the rifle, such that the projection of their common open area along the axis of the eye onto the cornea will form an entrance pupil to the eye which is horizontally elongated relative to its height, said entrance pupil having height and width dimensions. The width dimension of the entrance pupil is greater than the height dimension. The height dimension of the entrance pupil is of such a value that the entrance pupil is smaller than the pupil of the eye, and will cause the horizontal top edge of the front sight post and a horizontal edge of a target to be more sharply focused than if viewed with either the naked eye, or if viewed through an identical aperture which were presented to the eye in an orientation substantially perpendicular to the bore of the rifle. The width dimension of the entrance pupil is of such a value that the aperture is adapted to permit a sufficient amount of light to pass through the aperture so that the front sight post and the target are brighter than if they were viewed through an entrance pupil which was round and with a diameter equivalent to the height dimension of the entrance pupil.

In another aspect, the invention is a rifle having a receiver and a barrel, and having the rear aperture sight and the front sight post sight of any of the above descriptions mounted on the receiver and barrel, respectively.

In another aspect, the invention is the combination of the rear aperture sight and the front sight post sight of any of the above descriptions.

The entrance pupil created by the aperture of the rear sight can have a number of possible width-to-height aspect ratios, width and height dimensions, and shapes. The width dimension can be in a range of about 125% to about 500% of the height dimension; the width dimension can be in a range of about 150% to about 400% of the height dimension; the width dimension can be in a range of about 200% to about 300% of the height dimension. The height dimension can be in a range of about 0.010 inches to about 0.100 inches. The width dimension can be in a range of about 0.0125 inch to about 0.20 inch. The entrance pupil can be oval or elliptical shaped, slit shaped, like a cat's eye, rectangular shaped, rectangular shaped with radiused corners, and/or hexagonal shaped with vertices positioned at 3 o'clock and at 9 o'clock, etc. The apertures used to create the entrance pupil can be round, square, triangular, rectangular, elliptical, oval, and/or comprised of two overlapping circular holes whose centers are displaced horizontally from one another, etc.

The aperture plate can have different thicknesses. The thickness can be in the range of about 0.0005 inches to about 0.500 inches, the thickness can be in the range of about 0.001 inches to about 0.250 inches, the thickness can be in the range of about 0.002 inches to about 0.125 inches.

These above defined shapes of the entrance pupil to the eye can be created by creating an aperture in the aperture plate, or an aperture in an insert which is held by the aperture plate, such that the axis of the aperture or the axis of the insert is held at an angle different from perpendicular to the aperture plate, said aperture plate is then presented to the eye at an angle essentially perpendicular to the bore of the rifle barrel. As used in the claims, “an aperture plate having an aperture formed therein” shall be deemed to embrace an aperture formed in an insert which is held by the aperture plate.

These above defined shapes of the entrance pupil to the eye can be created by creating an aperture in an aperture plate, or an aperture in an insert which is held in an aperture plate, such that the axis of the aperture or the axis of the insert is substantially perpendicular to the aperture plate, said aperture plate is then presented to the eye at some inclination to the axis of the bore of the rifle barrel.

The invention thus provides a rear aperture sight for a rifle which creates an entrance pupil to the eye that is elongated horizontally relative to its height, and whose height is smaller than the pupil of the eye, so as to more sharply focus the horizontal top edge of the front sight post and the horizontal bottom edge of the target than if viewed by the unaided eye, while at the same time permitting sufficient light to pass therethrough, so that the front sight post and target are brighter than if viewed through a round aperture with a diameter equal to the entrance pupil height.

These, and other features and advantages of the present invention, will become more readily apparent during the following detailed description taken in conjunction with the drawings herein, in which:

BRIEF DESCRIPTION OF THE DRAWINGS OF THE INVENTION

FIG. 1 is a side view of a section of the human eye, comprising the cornea, the lens, the pupil, and the retina.

FIG. 2A is a side view similar to FIG. 1 and also showing an external aperture plate having an aperture which is larger than the pupil.

FIG. 2B is a side view similar to FIG. 2A but showing an external aperture plate having an aperture which is smaller than the pupil.

FIG. 3A is a side view similar to FIG. 1 and also showing an external aperture plate having an aperture where the aperture plate is inclined to the optical axis of the eye resulting in the projection of the aperture being smaller than the height of the pupil.

FIG. 3B is a view of the external aperture plate of FIG. 3A viewed in a direction along the optical axis of the eye.

FIG. 3C is a side view similar to FIG. 1 and also showing an external aperture plate having an aperture formed therein at some angle other than perpendicular thereto resulting in the projection of the aperture being smaller than the height of the pupil.

FIG. 3D is a view of the external aperture plate of FIG. 3C viewed in a direction along the optical axis of the eye.

FIG. 3E is a side view similar to FIG. 1 and also showing two external aperture plates each having an aperture resulting in the projection of the common open area of the apertures being smaller than the height of the pupil.

FIG. 3F is a view of the external aperture plates of FIG. 3E viewed in a direction along the optical axis of the eye.

FIG. 4 is a side view of the prior art U.S. Military rifle of the type M-16A2.

FIG. 4A is a rear perspective view of the prior art rear sight of the rifle of FIG. 4.

FIG. 4B is a side view of the prior art rear sight of the rifle of FIG. 4 showing the projection of the round aperture onto the cornea.

FIG. 4C is a partial cross-sectional view through the prior art front sight of the rifle of FIG. 4 along line 4C-4C in FIG. 4.

FIG. 5A is a side view of the prior art U.S. Military rifle of the type M-1 Garand.

FIG. 5B is a side cross-sectional view of the prior art rear sight of the rifle of FIG. 5A, set in the lower “zero” position to engage targets at under 200 yards.

FIG. 5C is a side cross-sectional view of the prior art rear sight of the rifle of FIG. 5A, set in the “high” position to engage targets beyond 200 yards.

FIG. 6A is a rearward looking oblique view of an eye looking through a round prior art larger aperture which is larger than the pupil.

FIG. 6B is a rearward looking oblique view of an eye looking through a round prior art smaller aperture which is smaller than the pupil.

FIG. 6C is a rearward oblique view of an eye looking through a horizontally elongated rectangular aperture as taught in application Ser. No. 11/619,953.

FIG. 7 is a sight picture looking through the sights of the rifle of FIG. 4 using the prior art large circular aperture rear sight.

FIG. 8 is a sight picture looking through the sights of the rifle of FIG. 4 using the prior art small circular aperture rear sight.

FIG. 9 is a sight picture looking through the sights of a rifle equipped with one embodiment of the present invention.

FIGS. 10A-D are sight pictures looking through the rear aperture sight of a rifle equipped with alternative embodiments of the present invention.

FIGS. 11A and 11B illustrate the geometry of another embodiment of the present invention.

FIG. 11C is a sight picture looking through the rear aperture sight of a rifle equipped with one embodiment of FIGS. 11A and 11B.

FIG. 11D is a sight picture looking through the rear aperture sight of a rifle equipped with another embodiment of FIGS. 11A and 11B.

FIG. 12A is a rearward oblique view of an eye looking through one embodiment of this invention, and shows a round aperture inclined at an angle to the optical axis of the eye projecting a horizontally elongated entrance pupil onto the cornea.

FIG. 12B is a rearward oblique view of an eye looking through another embodiment of this invention, and shows a square aperture inclined at an angle to the optical axis of the eye projecting a horizontally elongated entrance pupil onto the cornea.

FIG. 12C is a rearward oblique view of an eye looking through another embodiment of this invention, and shows two round vertically offset apertures projecting a horizontally elongated entrance pupil onto the cornea.

FIG. 12D is a rearward oblique view of an eye looking through another embodiment of this invention, and shows two oppositely directed and vertically offset triangular apertures projecting a horizontally elongated entrance pupil onto the cornea.

FIG. 13 is a side view of a rifle illustrating the line of sight of the eye, the axis of the rifle bore, and trajectory of a bullet fired from the rifle.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

Application Ser. No. 11/619,953 sets forth the benefits of a rear sight utilizing various designs of horizontally elongated apertures, all of which are created using an aperture plate, similar to that being used on an M-16 rifle, or one of it's derivative designs A2, A3, A4, M4, M4-A1, or similar rifles, such aperture plate being presented substantially perpendicular to the bore of the barrel and also substantially perpendicular to the axis of view of the shooter. The '953 application teaches that when a horizontally elongated aperture, whose height is less than the diameter of the pupil, is oriented with its axis substantially parallel to the optical axis of the eye, it will create a horizontally elongated entrance pupil to the eye of substantially the same size and shape as the aperture, and will thus aid the eye in focusing on the horizontal edge of the front sight post, and on the horizontal edge of the target, while allowing more light to pass than if the aperture were round with a diameter of the vertical dimension of the elongated aperture, thereby keeping the image brighter than the described round aperture would allow.

This continuation application teaches various methods by which a horizontally elongated entrance pupil can be created for the eye, by creating various forms of horizontally elongated apertures, which are presented in an aperture plate with the aperture plate being substantially perpendicular to the eye and the axis of the aperture being substantially parallel to and co-linear with the optical axis of the eye. This continuation application also teaches how a horizontally elongated entrance pupil can be created for the eye by methods other than by creating a horizontally elongated aperture in an aperture plate. These methods will create a horizontally elongated entrance pupil to the eye, so as to provide improved depth of field and improved focus on horizontal edges being viewed, while allowing more light to enter the eye, and creating a brighter image, than if a round aperture were used whose diameter is equal to the vertical dimension of the horizontally elongated aperture.

Referring to FIG. 1, is a functional illustration of a side cross section of the human eye 1, comprising the cornea 2, the lens 3, the retina 8, the pupil 4. Shown is the pupil's projection along the optical axis 9, of the eye 1, onto the cornea 2, forming the entrance pupil for an unaided eye. The projection of the entrance pupil is traced by rays 7. For the unaided eye, as illustrated, the diameter 6, of the entrance pupil is slightly greater than the diameter 5, of the pupil 4, due to the cornea acting as a converging lens. However, the proximity of the cornea 2, to the pupil 4, causes this difference in size to be small, and it can be ignored in the context of this current discussion. The diameter 5, of the pupil 4, can therefore be taken to be substantially the same as the diameter 6, of the entrance pupil created by projecting the pupil 4, along the optical axis 9, of the eye 1, onto the cornea 2. In the side view, as illustrated, the height of the projected entrance pupil is equal to the diameter 6, and this height will drive the vertical depth of field of the eye, determining the clarity with which horizontal features at varying distances can be seen.

FIG. 2A illustrates a side sectional view of an external aperture plate 10, comprising an aperture 11, and placed in front of the eye 1. Aperture plate 10, is positioned and oriented so that the axis 50, of the aperture 11, is co-linear with, and parallel to, optical axis 9 of the eye 1. In this illustrated example, aperture 11, is larger in the vertical axis than the diameter 6, of the pupil 4. The height 12, of projection 7, of the aperture 11, along the optical axis 9 of the eye 1, onto the cornea 2, is therefore larger than the pupil 4. Since it is the projection of the smallest aperture along the optical axis 9, onto the cornea 2, of the eye 1, that creates the dominant entrance pupil, in this illustrated case, the pupil 4, being smaller than the external aperture 11, will create the dominant entrance pupil to the eye 1, and the eye will receive no depth of field or focal benefit from the external aperture 11.

FIG. 2B illustrates an external aperture plate 10, comprising an aperture 11, and placed in front of the eye 1. Such aperture plate 10, being positioned and oriented so that the axis 50, of the aperture 11, is co-linear with, and parallel to, optical axis 9, of the eye 1. In this illustrated example, aperture 11, is smaller than the diameter 6 of the pupil 4. The height 12, of projection 7, of aperture 11, along the optical axis 9 of the eye 1, onto the cornea 2, is therefore smaller than the diameter 6, of the pupil 4. Since it is the projection along the optical axis 9, of the smallest aperture onto the cornea 2, of the eye 1, that creates the dominant entrance pupil, in this illustrated case, the projected opening 7, of aperture 11, will create the dominant entrance pupil to the eye 1, and the eye will receive a depth of field and focal benefit in the vertical axis from the external aperture 11.

FIGS. 2A and 2B therefore illustrate that for an aperture to provide a depth of field and focal benefit to the eye in the vertical axis, the height of the projected open area of the aperture must be smaller than the diameter of the pupil.

FIG. 3A illustrates one embodiment of this invention with a side sectional view of an eye 1, with an external aperture plate 10. Such aperture plate having a thickness 16, and comprising a round aperture 11, with diameter 12, formed with the axis 50, of aperture 11, substantially perpendicular to the face of the aperture plate 10. Said aperture plate 10, is positioned along the optical axis 9 of the eye 1, but oriented such that the axis 50, of aperture 11, is inclined at an angle 51, to the optical axis 9, of the eye 1. Such inclination causing the height 14, of the projection 7, of aperture 11, along the optical axis 9, of the eye 1, to be smaller than the diameter 6, of the pupil 4, and also smaller than the diameter 12, of aperture 11. In the vertical axis, it is therefore the entrance pupil created by the projection 7, of the open area of aperture 11, along the axis 9 of the eye, onto the cornea 2, that dominates the optical system, and in the vertical axis, the eye 1, gets a depth of field and focal benefit, from the entrance pupil created by the projected open area of external aperture 11. The vertical depth of field and focal benefit afforded by the entrance pupil height 14, will allow horizontal lines viewed by the eye to be more sharply defined than if they were viewed by the unaided eye, or if they were viewed through an aperture with diameter 12, while such aperture were oriented with its axis parallel to the optical axis 9 of the eye.

FIG. 3B illustrates a round aperture 11, presented with the aperture axis inclined at an angle to the axis of the eye, as described above in FIG. 3A, but viewed from the perspective of the eye. The open area of round aperture 11, projected towards the viewer, will form a slit-shaped entrance pupil 13. The entrance pupil 13, as seen by the viewer, has a height 14, and a width 15. Width 15, being greater than height 14. The exact shape and height and width dimensions of the slit-shaped opening 13, are determined by the geometric conditions of: 1) the diameter of round aperture 11, described by numeral 12, of FIG. 3A, and 2) the angle at which the axis of aperture 11, is inclined to the axis of the eye, described by numeral 51, of FIG. 3A, and 3) the thickness of the aperture plate, described by numeral 16, of FIG. 3A. If height 14, of entrance pupil 13, is smaller than the diameter of the pupil of the eye, the eye will realize a depth of field and focus benefit in the vertical axis, allowing horizontal lines to be viewed with greater clarity than if they were viewed with the unaided eye. However, since width 15, is greater than height 14, the image seen by the viewer will be brighter than if it were viewed through a round entrance pupil with diameter equivalent to height 14.

FIG. 3C illustrates another embodiment of the invention. An aperture plate 10, with thickness 16, comprises a round aperture 11, with diameter 12. Such aperture 11, is formed with the axis 50, of the aperture 11, oriented at an angle which is different from perpendicular to the face of the aperture plate 10. Aperture plate 10, is placed along the optical axis 9, of the eye 1, and oriented such that the face of aperture plate 10, is substantially perpendicular to the axis 9, of the eye, and also so aperture 11, has its axis 50, inclined at an angle 51, to the optical axis 9, of the eye 1. Such angle 51, being different from parallel to the optical axis 9, of the eye 1, and also being different from perpendicular to the face of aperture plate 10. The projection 7, of the aperture 11, along the optical axis 9, of the eye 1, onto the cornea 2, creates an entrance pupil which has a height 14. The entrance pupil height 14, is smaller than the height 6, of the entrance pupil created by the pupil 4, and also smaller than the diameter 12, of aperture 11. The entrance pupil created by the projection 7, of aperture 11, will therefore dominate the optical system in the vertical dimension, and the depth of field and focus realized by the eye in the vertical direction will be better than the depth of field that would be realized if an image were viewed by the unaided eye, and better than if an image were viewed through aperture 11, while the axis 50, of aperture 11, were parallel to, and collinear with, the optical axis 9, of the eye 1. The height 14 of the entrance pupil will be determined based on the diameter 12, of aperture 11, the angle 51, at which said aperture is inclined, and the thickness 16, of the aperture plate 10.

FIG. 3D illustrates the vertically compressed opening 13, of a round aperture 11, oriented as described in FIG. 3C, and as viewed by the eye. The vertically compressed opening has a width 15, and a height 14, said width being greater than said height. If height 14, is smaller than the diameter of the pupil of the eye, the eye will realize a depth of field and focus benefit in the vertical axis, allowing horizontal lines to be viewed with greater clarity than if they were viewed with the unaided eye, or if they were viewed through aperture 11, while the axis 50, of aperture 11, was oriented parallel to the axis of the eye.

It will be appreciated that many different shapes, other than round, which are not horizontally elongated, could be used for the aperture 11, as described in FIGS. 3A to 3D, yet by inclining the axis of the aperture to the optical axis of the eye, as described in these figures, all of these shapes which are not horizontally elongated would create an entrance pupil which was horizontally elongated. Square openings, vertically elongated rectangular openings, vertically elongated elliptical openings, vertically elongated oval openings, or other openings could all be created in an aperture plate, and such aperture plate could be inclined vertically relative to the optical axis of the eye, as described in FIGS. 3A to 3D, so as to create an entrance pupil which is wider than it is tall.

FIG. 3E illustrates round apertures 11 a, and 11 b, which are formed in aperture plates 10 a, and 10 b, respectively, such apertures having diameters 12 a, and 12 b, respectively, and being positioned with their respective axes 50 a, and 50 b, offset vertically from each other in a direction that is radial to the bore of the rifle, at a sufficient distance so the apertures 11 a, and 11 b, overlap. The projection 7, of the common open area of said apertures 11 a, and 11 b, along axis 9, of the eye 1, will create an entrance pupil of height 14, such height 14, being less than either diameter 12 a, or diameter 12 b, and also being less than the diameter 6, of pupil 4. The entrance pupil created by the projection 7, of the common open areas of apertures 11 a, and 11 b, will therefore dominate the optical system in the vertical dimension, and the depth of field and focus realized by the eye in the vertical direction will be better than the depth of field that would be realized if an image were viewed by the unaided eye, and better than if an image were viewed through apertures 11 a, and 11 b, while their axes 50 a, and 50 b, were collinear with each other, and also collinear with the optical axis 9, of the eye 1. The height 14, of the entrance pupil will be determined based on the diameters 12 a, and 12 b, of apertures 11 a, and 11 b, and also on the distance of separation between axes 50 a, and 50 b.

FIG. 3F illustrates the horizontally elongated entrance pupil 13, as described in FIG. 3E, but as viewed by the eye. Entrance pupil 13, is created by the projection of the common open area of two non-aligned round apertures, 11 a, and 11 b, which have their axes offset in a direction radial to the bore of the rifle. Horizontally elongated entrance pupil 13, has width 15, and height 14. Width 15, being greater than height 14. If height 14, is smaller than the diameter of the pupil of the eye, the eye will realize a depth of field and focus benefit in the vertical axis, allowing horizontal lines to be viewed with greater clarity than if they were viewed with the unaided eye, or if they were viewed through apertures 11 a, and 11 b, while their axes 50 a, and 50 b were collinear with each other, and also collinear with the optical axis of the eye. Since width 15, is greater than height 14, the image viewed through entrance pupil 13 will be brighter than if the image were viewed through a round entrance pupil, whose diameter was equivalent to height 14.

It will be appreciated that in FIGS. 3E to 3F, many different shapes other than round, could be used for the apertures 11 a, and 11 b, and by creating the described offset between the axes 50 a, and 50 b of said apertures, aperture shapes, which are not horizontally elongated, would create an entrance pupil which was horizontally elongated. Square openings, vertically elongated rectangular openings, vertically elongated elliptical openings, vertically elongated oval openings, or other openings could be created in aperture plates 10 a, and 10 b, and the overlap of such aperture plates, as described in FIGS. 3E to 3F, would create an entrance pupil which is wider than it is tall.

FIG. 4 shows the United States military M16A2 service rifle 17, comprising, generally, lower receiver 18, upper receiver 19, pistol grip 20, buttstock 21, barrel 22, handguard 23, front sight assembly 24, and rear sight assembly 26.

FIG. 4A shows the prior art rear sight assembly 26, in more detail. Sight assembly 26, comprises a flip type dual aperture plate 28, having a smaller aperture 30, having a diameter of about 0.070 inches for longer ranges, and a larger aperture 32, having a diameter of about 0.200 inches for shorter ranges. A windage knob 34, is used to adjust the windage of the rear sight assembly 26. An elevation knob 36, is used to adjust the elevation of the rear sight assembly 26, for ranges beyond 200 meters.

FIG. 4B shows the prior art rear sight assembly 26, in a partial section side view. It shows how the aperture plate 28, is presented to the shooter at an angle substantially perpendicular to the optical axis 9, of the eye, and the aperture 30, formed in said aperture plate is formed with the axis of the aperture substantially parallel to, and aligned with, the optical axis 9, of the eye. Such aperture 30, projecting an entrance pupil 80, onto the cornea 2.

FIG. 4C shows the prior art front sight assembly 24 in more detail. It comprises a post 38 which is adjustable but which is only used to initially zero the rifle. (As used herein, the term “post” shall be deemed to embrace any front sight aiming device, such as posts, pins, blades, etc.) The post 38 has a horizontal top edge 40 and vertical side edges 42, 42.

FIG. 5A shows the United States military M-1 service rifle 60, comprising, generally, the stock 61, front sight 62, rear sight assembly 63, aperture plate 65, sight base 68, cover plate 69, barrel 71, receiver 72, sight adjustment knob 73.

FIG. 5B shows a side view sectional detail of the rear sight assembly 63 in the low position, for engaging targets at a close range of under 200 yards, showing the position of the eye 1, the axis of the eye 9, the aperture plate 64, the round 0.069 inches diameter aperture 64, the axis of the aperture 50, the sight base 63, the elevation pinion gear 67, the aperture rack 66, the axis 70, of rotation for the aperture rack, and the cover plate 68. In this configuration, the axis 9 of the eye and the axis 50, of the aperture 64, are substantially parallel and co-linear, and the entrance pupil 80, projected onto the eye by the round aperture 64, is substantially the same shape as the aperture itself.

FIG. 5C shows a similar side view sectional detail of the rear sight assembly as FIG. 5B, however the round aperture is set in the high position for engaging targets at long range. In this configuration, the aperture plate 64, is inclined forward, so the axis 50, of the round aperture 64, subtends an angle 51, relative to the axis 9, of the eye. This angle of forward inclination can be up to maximum of approximately 15 degrees. In the configuration of maximum forward inclination, the round aperture 64, will project an entrance pupil 80, along the optical axis 9, onto the cornea 2, which has the form of a horizontally elongated slit shape, such slit shape of the entrance pupil 80, having a width dimension of approximately 0.069 inches, that being approximately the same dimension as the diameter of aperture 64, but having a reduced height dimension of 0.061 inches, such width dimension being up to 113% of the height dimension. The relationship between the height dimension and the width dimension being driven by the thickness of the aperture 16, and the angle of inclination 51.

FIG. 6A shows a rear looking oblique view of the prior art, showing a dual leaf style aperture plate 28, of design similar to that used in the United States military rifle M-16/A2 or similar, utilizing a large aperture 32, intended for close quarters battle, and for engaging targets at under 200 meters, such aperture plate 28, being presented substantially perpendicular to the axis 9, of the eye 1, and the axis 50, of the large aperture 32, being oriented substantially parallel to the optical axis 9, of the eye 1. The projection 7, of large aperture 32, along the optical axis 9, onto the cornea 2, of eye 1, creates an entrance pupil 80, which is substantially identical in size and shape to the large aperture 32. Such entrance pupil being larger than the pupil 4, of the eye 1, large aperture 32, will not provide a focus benefit to the shooter.

FIG. 6B shows a rear looking oblique view of the prior art, showing a dual leaf style aperture plate 28, of design similar to that used in the United States military rifle M-16/A2 or similar, utilizing a smaller aperture 30, intended for engaging targets at over 200 meters, such aperture plate 28, being presented substantially perpendicular to the axis 9 of the eye 1, and the axis 50, of the smaller aperture 30, being oriented substantially parallel to the optical axis, 9, of the eye 1. The projection 7, of smaller aperture 30, along the optical axis 9, onto the cornea 2, of eye 1, creates an entrance pupil 80, which is substantially identical in size and shape to the smaller aperture 30. Such entrance pupil being smaller than the pupil 4, of the eye 1, smaller aperture 30, will provide a focus benefit to the shooter, and will also cause a reduction of light transmission to the eye thereby dimming the image seen by the eye.

FIG. 6C shows a rear looking oblique view of the invention of application Ser. No. 11/619,953, showing a dual leaf style aperture plate 28, of design similar to that used in the United States military rifle M-16/A2, or derivative designs, utilizing a horizontally elongated rectangular aperture 31, such horizontally elongated rectangular aperture 31, having a width and a height. Said height is smaller than the diameter of the pupil 4, said width is greater than said height. Aperture plate 28, is presented substantially perpendicular to the axis 9, of the eye 1, and the axis 50, of the horizontally elongated rectangular aperture 31, being oriented substantially parallel to the optical axis, 9, of the eye 1. The projection 7, of horizontally elongated rectangular aperture 31, along the optical axis 9, onto the cornea 2, of eye 1, creates a horizontally elongated entrance pupil 80, which is substantially identical in size and shape to the horizontally elongated rectangular aperture 31. Such horizontally elongated entrance pupil 80, having a width and a height, said height, being smaller in height than the pupil 4, of the eye 1, horizontally elongated entrance pupil 80, will provide a focus benefit to the shooter in the vertical axis, causing the horizontal edges of the front sight and the horizontal edges of the target to be in sharper focus than if viewed through the unaided eye. Said width of the horizontally elongated entrance pupil 80, being greater than said height of the horizontally elongated entrance pupil 80, the horizontally elongated entrance pupil 80, will allow more light into the eye 1, than if the entrance pupil were round, and of the diameter equivalent to the height of the rectangular aperture 31.

FIG. 7 shows the sight picture when aiming at a bull's eye target 54, with the post 38 and large aperture 32. The horizontal top edge 40 and vertical side edges 42, 42 of the post 38, as well as the target edge within and outside the aperture 32, appear fuzzy, or out of focus. Thus, precise alignment of the horizontal top edge 40 of the post 38 with the lower edge of bull's eye 54, i.e. a precise 6 o'clock hold, is not possible.

FIG. 8 shows the sight picture when aiming at the bull's eye 54 with the post 38, and small aperture 30. The horizontal top edge 40 and vertical side edges 42, 42, of the post are sharply focused. However, the smaller aperture permits less light to pass through the aperture. Thus, even though the horizontal top edge 40, and vertical side edges 42, 42, of the front sight post 38, and target, are clearly focused, the front sight post 38, and bull's eye 54, are nevertheless dim, thus negating the positive effects on accuracy from the clearly focused front sight post 38.

FIG. 9 illustrates a rear aperture sight 31, for a rifle according to the principals of the invention. The sight 31, can be a leaf 28, which is adapted to be mounted to the rifle 17, (or to any other rifle). The sight leaf 28, has a horizontally elongated aperture 31, formed therein having height h and width w dimensions. The width w is greater than the height h. The height h is of such a value that the aperture 31, is adapted to cause the horizontal top edge 40, of the front sight post 38, and the horizontal edge of the target 54, to be sharply focused, thereby permitting precise alignment of the horizontal top edge 40, with the lower edge of the bull's eye 54. The width w is of such a value that the aperture 31, permits a sufficient amount of light to pass therethrough so that the front sight post 38, and bull's eye 54, are bright. The focus of the vertical side edges 42, 42, of the front sight post 38, and of the vertical edges of the target 54, is sacrificed, and they appear fuzzy or out of focus. However, it has been determined that this is of minor consequence, as it suffices for the shooter to simply center the two vertical side edges 42, 42, albeit blurry, relative to the bull's eye 54. The shooter does not need to precisely line up either of these edges with the bull's eye, as is the case for the top edge of the post.

Preferably, for a horizontally elongated aperture, the width w is in a range of about 110% to about 500% of the height h. More preferably, the width w is in a range of about 120% to about 300% of the height h. Most preferably, the width w is in a range of about 140% to about 160% of the height h. Other width w to height h aspect ratios can of course be used, and the invention is not to be limited to the values specified herein.

Preferably, for a horizontally elongated aperture, the height h is in a range of about 0.010 inches to about 0.100 inches. Preferably, the width w is in a range of about 0.011 inches to about 0.20 inches. Other width w and height h dimensions can of course be used, and the invention is not to be limited to the values specified herein.

The aperture 31, can be rectangular shaped as shown in FIG. 9. Alternatively, the aperture can be rectangular shaped with radiused corners as shown at 13 a in FIG. 10A, oval shaped as shown at 13 b in FIG. 10B, hexagonal shaped with vertices positioned at 3 o'clock and at 9 o'clock as shown at 13 c in FIG. 10C, or elliptical shaped as shown at 13 d in FIG. 10D. Other shapes can of course be used, and the invention is not to be limited to the shapes specified herein.

Referring now to FIG. 11A, there is illustrated the geometry for another embodiment of the invention. A circle has a radius R. A circular segment s thereof has a corresponding chord c as defined by included angle θ. Chord c=2R(sin(θ/2)); segment s has a height h=R−R(cos(θ/2)). As shown in FIG. 11C, aperture 13 e can be formed by two circular segments having chords of equal length positioned such that their chords are co-liner and oriented horizontally. In this case, and referring to FIG. 11B, c1=c2=w, and the total height hT of the two chords c1 and c2 (and hence of the aperture 13 e) is hT=h1+h2 where h1=h2. R and θ are selected such that, as before, the height hT is in a range of about 0.010 inches to about 0.100 inches, and the width w is in a range of about 0.011 inches to about 0.20 inches. While illustrated as being from two circles each having the same radius R, the aperture formed by the two circular segments could just as well be from two circles having differing radii. Referring still to FIG. 11B, the FIG. 11C aperture 13 e can be defined as the area (shaded portion) bounded by and common to two overlapping circles having differing radii R1 and R2. The circles intersect at points X and Y. The line XY formed by their intersection points falls between the centers of the two circles A and B. R1, R2, θ1, and θ2 are selected such that, as before, the height hT is in a range of about 0.010 inches to about 0.100 inches, and the width w is in a range of about 0.011 inches to about 0.20 inches.

Alternatively, with the chords c1 and c2 oriented vertically as in FIG. 11B, the aperture could be formed by the combined area of the two circles and the common overlapping portions of the circles (i.e. the shaded portion plus the unshaded portion of FIG. 11B). See aperture 13 f in FIG. 11D. In this case, the width w of the aperture is the distance between the two centers A and B of the circles, plus the sum of the two radii R1 and R2 of the two circles, or w=AB+R1+R2. And, the height h of the aperture is either twice R1 or twice R2, whichever one (of R1 and R2) is greater. In any event, AB, R1, and R2 are selected such that the height h is in a range of about 0.010 inches to about 0.100 inches, and the width w is in a range of about 0.011 inches to about 0.20 inches.

FIG. 12A shows a rear looking oblique view of another embodiment of this invention, whereby an aperture plate 10, has a round aperture 11, formed therein. Aperture plate 10, is presented to the eye such that the axis 50, of the aperture 11, is inclined at an angle 51, to the axis 9, of the eye 1. In this orientation, the projection 7, the open area of aperture 11, along the optical axis 9, of the eye 1, onto the cornea 2, will create an entrance pupil 80, that is a slit shape which is horizontally elongated relative to its height. Said entrance pupil 80, having a width and a height. Said width being greater than said height, said height being smaller than the pupil 4, of the eye. Said horizontally elongated slit shaped entrance pupil 80, will provide a focus benefit to the shooter in the vertical axis, causing the horizontal edges of the front sight and the horizontal edges of the target to be in sharper focus than if viewed through the unaided eye. Said width of the horizontally elongated entrance pupil 80, being greater than said height, will allow more light into the eye than if the entrance pupil were round, and of the diameter equivalent to the height of the horizontally elongated entrance pupil 80, thereby increasing the image brightness.

FIG. 12B shows a rear looking oblique view of an alternate execution of an embodiment of this invention, whereby an aperture plate 10, has an aperture 11, of a substantially square shape formed therein. The aperture 11, is not horizontally elongated, having substantially equal height and width. Aperture plate 10, is presented inclined to the optical axis 9 of the eye 1, such that the axis 50, of the square aperture 11, is inclined vertically at an angle 51, to the axis 9 of the eye. In this orientation, the projection 7, of the open area of aperture 11, along the optical axis 9, of the eye 1, onto the cornea 2, will form a horizontally elongated rectangular entrance pupil 80. Such horizontally elongated rectangular entrance pupil 80, having a width and a height, said height, being smaller than the pupil 4 of the eye, entrance pupil 13 will provide a focus benefit to the shooter in the vertical axis, causing the horizontal edges of the front sight and the horizontal edges of the target to be in sharper focus than if viewed through the unaided eye. Said width of the entrance pupil 80, being greater than said height, will allow more light into the eye than if the entrance pupil were round and of the diameter equivalent to the height of the entrance pupil 80, thereby increasing the image brightness.

FIG. 12C shows a rear looking oblique view of another embodiment of this invention, whereby at least two aperture plates 10 a, and 10 b, each having an aperture 11 a, and 11 b, formed therein, are presented to the eye such that the axes 50 a, and 50 b, of apertures 11 a, and 11 b, respectively, are offset in a direction vertical to the optical axis 9 of the eye, by a distance such that the projection 7, of the common open area of said apertures 11 a, and 11 b, along the optical axis 9, of the eye 1, onto the cornea 2, will form a horizontally elongated slit shaped entrance pupil 80. Such entrance pupil 80, having a width and a height, said height, being smaller than the pupil 4, of the eye 1, the entrance pupil 80, will provide a focus benefit to the shooter in the vertical axis, causing the horizontal edges of the front sight and the horizontal edges of the target to be in sharper focus than if viewed through the unaided eye. Said width of the entrance pupil 80, being greater than said height, entrance pupil 80, will allow more light into the eye than if the entrance pupil were round and of the diameter equivalent to the height of the entrance pupil 80, thereby increasing the image brightness.

FIG. 12D shows a rear looking oblique view of another embodiment of this invention, whereby at least two aperture plates 10 a, and 10 b, each having differently shaped apertures 11 a, and 11 b, formed therein, for example, two oppositely directed and vertically offset triangular apertures, are presented to the eye 1, such that the projection 7, of the common open area of said apertures 11 a, and 11 b, along the optical axis 9, of the eye 1, onto the cornea 2, will form a horizontally elongated entrance pupil 80. Such entrance pupil 80, having a width and a height, said height, being smaller than the pupil 4 of the eye, the entrance pupil 80, will provide a focus benefit to the shooter in the vertical axis, causing the horizontal edges of the front sight and the horizontal edges of the target to be in sharper focus than if viewed through the unaided eye. Said width of the entrance pupil 80, being greater than said height, will allow more light into the eye than if the entrance pupil were round and of the diameter equivalent to the height of the entrance pupil 80, thereby increasing the image brightness.

The horizontally elongated entrance pupils created by the invention of FIGS. 12A-12D will have width w, and height h. Preferably, the width of the entrance pupil w, is in a range of about 125% to about 500% of the height h. More preferably, the width w, is in a range of about 150% to about 400% of the height h. Most preferably, the width w, is in a range of about 200% to about 300% of the height h. Other width w, to height h, aspect ratios can of course be used, and the invention is not to be limited to the values specified herein.

Preferably, the height of the entrance pupil h, is in a range of about 0.010 inches to about 0.100 inches. Preferably, the width of the entrance pupil w, is in a range of about 0.011 inches to about 0.20 inches. Other width w, and height h, dimensions can of course be used, and the invention is not to be limited to the values specified herein.

The entrance pupil 80, can be slit shaped, as shown in FIG. 12A or FIG. 12C. Alternatively, the entrance pupil can be rectangular shaped, as shown in FIG. 12B, or hexagonal shaped, with vertices positioned at 3 o'clock and at 9 o'clock, as shown in FIG. 12D. Other shapes of entrance pupils can be created by varying the shapes of the apertures, the number of aperture plates used, the inclination of the aperture axis to the optical axis of the eye, the thickness of the aperture plates, and the degree of offset between the aperture axis and the optical axis of the eye. The invention is not to be limited to the shapes specified herein.

FIG. 13 is a side view of a rifle, comparing the axis of the eye 9, aligned through the aperture 11, and past the front sight post 38, to the target 54, versus the axis of the bore 52, such that the trajectory of the bullet 53, intersects the axis of the eye 9, at the target 54.

Those skilled in the art will readily recognize numerous adaptations and modifications which can be made to the present invention which will result in an improved aperture sight for a rifle, yet all of which will fall within the spirit and scope of the present invention as defined in the following claims. For example, the rear sight could be any structure capable of having an aperture formed therein, and not just the aperture plate shown in the drawings. Accordingly, the invention is to be limited only by the scope of the following claims and their equivalents. 

1. A rear aperture sight for use in conjunction with a front sight post sight on a rifle, the front sight post having a horizontal top edge and vertical side edges, said rear aperture sight comprising: a rear sight adapted to be mounted on the rifle, said rear sight having a horizontally elongated aperture formed therein having a height h and a width w, said width w being greater than said height h, said height h being of such a value that said aperture is adapted to cause the horizontal top edge of the front sight post and a horizontal edge of a target to be sharply focused, said width w being of such a value that said aperture is adapted to permit a sufficient amount of light to pass therethrough so that the front sight post and the target are bright, wherein said aperture is defined by two circular segments s1 and s2 having chords c1 and c2, respectively, defined by included angles θ1 and θ2, respectively, of circles having radii R1 and R2, respectively, said chords c1 and c2 having heights h1 and h2, respectively, wherein said radii R1 and R2 and said angles θ1 and θ2 are selected such that said chords c1 and c2 are of equal length, wherein said circular segments are positioned such that said chords c1 and c2 are co-linear and oriented horizontally.
 2. The sight of claim 1 wherein R1=R2=R and θ1=θ2=θ.
 3. The sight of claim 1 wherein R1=R2 and θ1≠θ2.
 4. The sight of claim 1 wherein w=c1=c2, w being in a range of about 0.011 inch to about 0.20 inch, and wherein h=h1+h2, h being in a range of about 0.010 inch to about 0.100 inch.
 5. A rear aperture sight for use in conjunction with a front sight post sight on a rifle, the front sight post having a horizontal top edge and vertical side edges, said rear aperture sight comprising: a rear sight adapted to be mounted on the rifle, said rear sight having at least one aperture plate, said at least one aperture plate having an aperture formed therein, said aperture defining an entrance pupil for an eye of a shooter of the rifle, said entrance pupil being horizontally elongated, said horizontally elongated entrance pupil having a height h and a width w, said width w being at least about 125% of said height h, said height h being smaller than a diameter of a pupil of the eye of the shooter and of such a value that said entrance pupil is adapted to cause the horizontal top edge of the front sight post and a horizontal edge of a target to be more sharply focused than if viewed by an unaided eye, said width w being of such a value that an area defined by said entrance pupil is greater than an area defined by a circular entrance pupil having a diameter equal to said height h, thereby permitting more light to pass through said entrance pupil than through the circular entrance pupil, and causing the front sight post and the target to appear brighter than if viewed through the circular entrance pupil.
 6. The sight of claim 5 where said at least one aperture plate is a single aperture plate having a circular aperture formed therein, said circular aperture having an axis, said aperture plate adapted to be mounted relative to the rifle such that said circular aperture axis is inclined at an angle relative to a bore of a barrel of the rifle.
 7. The sight of claim 6 wherein said circular aperture is formed in said aperture plate such that said circular aperture axis is substantially perpendicular to said aperture plate, and said aperture plate is adapted to be mounted relative to the rifle such that said aperture plate is inclined at an angle relative to the bore of the barrel of the rifle.
 8. The sight of claim 6 wherein said circular aperture is formed in said aperture plate such that said circular aperture axis is inclined at an angle relative to said aperture plate, and said aperture plate is adapted to be mounted relative to the rifle such that said aperture plate is substantially perpendicular relative to the bore of the barrel of the rifle.
 9. The sight of claim 5 wherein said at least one aperture plate is at least two aperture plates, each said aperture plate having an aperture formed therein, and wherein said at least two aperture plates are offset vertically such that their common open areas define said entrance pupil.
 10. The sight of claim 9 wherein said apertures are circular.
 11. The sight of claim 9 wherein said apertures are square.
 12. The sight of claim 9 wherein said apertures are triangular, and wherein said triangular apertures are inverted relative to one another.
 13. The sight of claim 5 wherein said at least one aperture plate is a transparent substrate and said aperture is formed by adding an opaque mask to said transparent substrate.
 14. The sight of claim 5 wherein w is in a range of about 0.0125 inches to about 0.20 inches, and wherein h is in a range of about 0.010 inches to about 0.100 inches.
 15. The sight of claim 5 wherein said width w is in a range of about 125% to about 500% of said height h.
 16. The sight of claim 5 wherein said width w is in a range of about 150% to about 400% of said height h.
 17. The sight of claim 5 wherein said width w is in a range of about 200% to about 300% of said height h.
 18. The sight of claim 5 wherein a geometric shape of said entrance pupil is selected from a group of geometric shapes consisting of ovals, ellipses, rectangles, and hexagons.
 19. The sight of claim 5 wherein a geometric shape of said aperture is selected from a group of geometric shapes consisting of circles, squares, rectangles, triangles, ellipses, and ovals.
 20. The sight of claim 5 wherein said at least one aperture plate has a thickness in a range of about 0.0005 inches to about 0.500 inches.
 21. The sight of claim 5 wherein said at least one aperture plate has a thickness in a range of about 0.001 inches to about 0.250 inches.
 22. The sight of claim 5 wherein said at least one aperture plate has a thickness in a range of about 0.002 inches to about 0.125 inches.
 23. A rifle having a receiver and a barrel, said rifle comprising: A front sight post mounted on said barrel of said rifle, said front sight post having a horizontal top edge and vertical side edges, a rear sight mounted on said receiver of said rifle, said rear sight having at least one aperture plate, said at least one aperture plate having an aperture formed therein, said aperture defining an entrance pupil for an eye of a shooter of said rifle, said entrance pupil being horizontally elongated, said horizontally elongated entrance pupil having a height h and a width w, said width w being at least about 125% of said height h, said height h being smaller than a diameter of a pupil of the eye of the shooter and of such a value that said entrance pupil is adapted to cause said horizontal top edge of said front sight post and a horizontal edge of a target to be more sharply focused than if viewed by an unaided eye, said width w being of such a value that an area defined by said entrance pupil is greater than an area defined by a circular entrance pupil having a diameter equal to said height h, thereby permitting more light to pass through said entrance pupil than through the circular entrance pupil, and causing said front sight post and the target to appear brighter than if viewed through the circular entrance pupil.
 24. A combination rear aperture sight and front sight post for use on a rifle, said combination comprising: a front sight post adapted to be mounted on a barrel of the rifle, said front sight post having a horizontal top edge and vertical side edges, a rear sight adapted to be mounted on the rifle, said rear sight having at least one aperture plate, said at least one aperture plate having an aperture formed therein, said aperture defining an entrance pupil for an eye of a shooter of the rifle, said entrance pupil being horizontally elongated, said horizontally elongated entrance pupil having a height h and a width w, said width w being at least about 125% of said height h, said height h being smaller than a diameter of a pupil of the eye of the shooter and of such a value that said entrance pupil is adapted to cause said horizontal top edge of said front sight post and a horizontal edge of a target to be more sharply focused than if viewed by an unaided eye, said width w being of such a value that an area defined by said entrance pupil is greater than an area defined by a circular entrance pupil having a diameter equal to said height h, thereby permitting more light to pass through said entrance pupil than through the circular entrance pupil, and causing said front sight post and the target to appear brighter than if viewed through the circular entrance pupil. 